1. Field of the Invention
This invention relates to a photointerrupter of the type which comprises a resinous hollow holder case housing a light emitting element and a light receiving element as opposed to each other.
2. Description of the Related Art
As is well known, a photointerrupter includes, in combination, a light emitting element such as a light emitting diode (LED) and a light receiving element such as a photodiode arranged in opposition to the light emitting element with a suitable spacing. Normally, the light beam generated by the light emitting element reaches the light receiving element. However, if the light beam is interrupted by passage of an object between the two photo elements for example, the light receiving element detects such interruption.
The combination of light emitting and receiving elements may be housed in a hollow holder case which is made of a synthetic resin. The respective photo elements may be fixed in place within the holder case by adhesive bonding, as disclosed in Japanese Utility Model Publication No. 3(1991)-49404 (Published: Oct. 22, 1992) for example.
However, the adhesive bonding is disadvantageous for inefficiency of applying and curing the adhesive. Further, the adhesive bonding is also disadvantageous in that the adhesive may be unexpectedly deposited on the operative surfaces of the respective photo elements. Morever, heat necessary for curing the adhesive may damage one or both of the photo elements.
On the other hand, the Japanese utility model publication also discloses an opposite pair of elastic stoppers integral with the holder case for fixing the respective photo elements. Specifically, the elastic stoppers are arranged and configured such that they are elastically deformed upon insertion of the photo elements into the holder case but restore to their original position into fixing engagement with the thus inserted photo elements. Thus, the provision of the elastic stoppers eliminates the problems encountered by the adhesive bonding. However, the use of the elastic stoppers is still disadvantageous in the following respects.
(1) Due to the presence of the elastic stopper, a mold used for forming the resinous holder case needs to have a relatively complicated configuration, thus resulting in a production cost increase.
(2) The provision of the elastic stoppers will inevitably results in an size increase of the holder case (namely, the photointerrupter itself).
(3) Since the respective photo elements are fixed in place only by the elasticity of the elastic stoppers, the photo elements may unexpectedly displace due to the elasticity of the stoppers, consequently resulting in improper operation of the photointerrupter.
(4) The presence of the elastic stoppers hinders automation with respect to assembly of the photointerrupter, consequently resulting in a production cost increase combined with the complication of the mold.